The maple industry has produced maple syrup in the traditional way for about a hundred years until about the decade 1960 to 1970. Thereafter, it has undergone a transformation towards industrialization in order to cut production costs that became prohibitive. In the 60s, collecting maple sap was still done through buckets hanging from maple trees. Then in the 70s, sap collection was done through a network of tubing and gravity flow, then through vacuum systems. All to increase yields for collecting maple sap.
The syrup which is made by boiling the sap in the spring, contains suspended solids that appear during evaporation and cooking maple sap, which reduces the volume of water from 30% to 50% to give a syrup 66% sugar (Brix) and 34% water.
During collection, the average percentage of sugar in the sap varies from 1% to 5% depending on the type and age of trees. One must therefore remove a large volume of water to obtain a 66% concentrate of sugar syrup (Brix). The boiling volume can be reduced by using a method of nano filtration membrane commonly known as reverse osmosis.
Up to 90% of water molecules (H20) are removed, while retaining in the concentrate all the mineral/particles and the specific sap molecules. During the evaporation process certain particles from wood fiber (the tree) will appear as residues giving an acrid taste and blurred maple syrup product. So to improve quality, one must get rid of these suspended solids to obtain crystal clear syrup by filtration through a filter of 5-100 micro according to degree of clarity that is desired.
These materials, known as in the popular jargon as “sugar sand”, which must be removed when the syrup comes out of the evaporator at 219 F or 104 C.
In the 1900s this filtration was done through a felt fabric installed above a circular container by gravity filtration. In time, this was replaced until today by cylindrical or plate presses, wherein filter papers or various membranes are inserted and which are supported by grooved plates in order to withstand the pressure of hot syrup (about 60 psi). FIG. 1 illustrates an example of a standard press. Under this pressure the fine particles present in the hot syrup rapidly clog the filter papers or filter membranes.
One way to solve this problem is to add an agglomerating powder which is used to capture suspended solids in the syrup. This powder is extremely fine diatomaceous earth consists of marine products (degradation product of crustaceans). It must be added constantly to increase the volume of syrup filtered prior to disassembly of the press, during a period of 30 minutes to 3 hours before disassembly, which varies from the start to the end of the sugaring season. There is no other solution than to disassemble the press and change the filter membranes several times during a day of production.